The present invention relates to a call detection control apparatus for a subscriber circuit of a telephone switching system.
In a subscriber circuit of a conventional telephone switching system, as shown in FIG. 7, power is supplied from a power supply circuit 3 to all individual call detecting circuits 10 to 12 respectively prepared for telephone subscriber lines 30 to 32 regardless of whether each subscriber is engaged in speech communication, thereby always monitoring for a call signal that originates from each of the telephone subscriber lines.
Recently, such a call detecting circuit has been realized by an electronic circuit constituted by a semiconductor element and the like in consideration of size, weight, economy, durability, operating speed, and the like. Owing to the nature of this circuit, bias power is constantly supplied to the circuit, and hence the circuit operates while always consuming a bias current.
Since power is constantly supplied to this conventional call detection control apparatus, power is wasted in the individual call detecting circuits 10 to 12 even in an on-hook state. Therefore, with an increase in the number of telephone subscriber lines, the power consumption is increased.